RAVEN a drastically improved design for a recoilless rifle. In a traditional recoilless rifle, at the moment of ignition gas is free to exit the rear of the gun out of a De Laval nozzle:

If the thrust of gas going through the nozzle is close enough to the momentum of the gas and projectile exiting the muzzle, the weapon is recoilless or close enough to. The problem is that this is hideously inefficient; most of the propellant mass is used to counteract projectile momentum instead of pushing the projectile.

In the RAVEN, the breech is closed to gas flow at the moment of firing:

But it is opened shortly afterward, while the projectile is still in-bore. The wave cause by the sudden drop in pressure due to the breech vents opening cannot catch up with the projectile in time to affect it, so there is no velocity loss and the recoil reduction is essentially free.

Timing of the opening of the breech is most easily achieved by a blowback breech, IMO. The acceleration of a delay mass should be extremely repeatable, and could easily give consistent timing. The vent holes and nozzle will likely be consumable items, just as they are in traditional recoilless rifles.

Unlike traditional recoilless rifles, which are limited to low-to-medium velocities due to their inefficiency, RAVEN works better with high velocities, since the projectile will be moving a higher percentage of the speed of sound of the propellant gas, and so venting can occur earlier. Furthermore, in high velocity weapons the momentum of the gas at the muzzle is a higher percentage of total recoil, so the percentage reduction of recoil will be higher.

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I think there is something missing, there should be some sort of small nuance that ruin this weapon system, which is a reason why nobody bothers to actually produce those. I think there is some sort of technical limitation that make this weapon not fit for service.

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I think there is something missing, there should be some sort of small nuance that ruin this weapon system, which is a reason why nobody bothers to actually produce those. I think there is some sort of technical limitation that make this weapon not fit for service.

The clear problem is that it wasn't designed by superior teutonic engineers.

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I think there is something missing, there should be some sort of small nuance that ruin this weapon system, which is a reason why nobody bothers to actually produce those. I think there is some sort of technical limitation that make this weapon not fit for service.

There is.

Here's part of it-

The pictured gun would launch a 28 pound HESH round to ~1500 FPS. Note the size of the fireball out it's ports.

Now, think of something producing ~3X higher velocites, and a corresponding puff out the backside. That's a BIIG "danger zone" to deal with.

Dealing with port erosion I suspect is another limiting factor, unless the ports are incorporated into the shell somehow and hence "consumable"..

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Jeez, you guys are terrible at marketing. Don't look at the back blast as a drawback. Instead, consider it a feature Not only does the gun help destroy the enemy, it provides illumination at the same time!

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The gun on a stick in the first link is one of the greatest things I've ever seen. Integrating it on an autocannon looks quite doable given the trend towards unmanned turrets, and their swinging breech looks a lot like the CTA 40 breech. Not that IFV's care about recoil or long term sustained fire with the limited ammo load of a large calibre IFV, but I'm sure they could find something that would appreciate it.

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Come to think of it, you'd want the wear component of the vent to be on the case anyhow, because you'd need to have different strength burst valves or whatever on different cartridges to achieve different timing. Optimal timing for APFSDS will be different than optimal timing for HE-FRAG.

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The pictured gun would launch a 28 pound HESH round to ~1500 FPS. Note the size of the fireball out it's ports.

Now, think of something producing ~3X higher velocites, and a corresponding puff out the backside. That's a BIIG "danger zone" to deal with.

Dealing with port erosion I suspect is another limiting factor, unless the ports are incorporated into the shell somehow and hence "consumable"..

Simple solution: simply turn it around for close range flamethrowing action!

"Close range flamethrowing action!" is a trademark of the stupid ideas corporation. Warning: flamethrowing has been shown to result in a number of medical issues including: first degree burns, second degree burns, third degree burns, hair loss, skin loss, ignition of subcutaneous fat, asphyxia, uncontrolled bowel movements, cataracts and death. Flamethrowing should only be done in a carefully controlled environment and under adult supervision. Use at own risk.

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Come to think of it, you'd want the wear component of the vent to be on the case anyhow, because you'd need to have different strength burst valves or whatever on different cartridges to achieve different timing. Optimal timing for APFSDS will be different than optimal timing for HE-FRAG.

We must move more wear components into the case! Bring on the single shot preloaded barrels!

I'm also fascinated by RAVEN and it has many nifty implications regarding 'light weight without losing performance' as far as recoilless technologies go. One was for improving man portable firepower (mentioned in the first pdf Collimatrix posted in the original post.

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First off, notice the "might" in the title. It is not yet known what exactly happened. What I'll be talking about is something I heard from someone close to the people involved. It might turn out to be not true, or it might be true. To be sure we have to wait for the official report of the investigation.

Second, it might seem I am attacking the victims of the accident, this is not the case. But if they made mistakes, I will point them out.

So most of you have probably already heard of the accident with the M18 Hellcat. What I have heard from people close, is that the round went off when they opened the breech after a misfire, or slightly after they opened the breech. So, a misfire huh. Nasty stuff when it involves explosives.

So, what happened?

Well, misfires happen. There's nothing strange about that. I assume a lot of you have experienced misfires with small arms, and you know the procedure of dealing with them. But with misfires like these are handled (completely) differently. I asked around a bit, and apparently the gunner waited a few minutes after the misfire before he opened the breech. This is good, but not good enough. Not by a long shot. If I remember correctly, when your small arms firearm misfires you keep the barrel pointing down range for at least 30 seconds. After 30 seconds you can safely assume the round will not go off by itself. It's different when a proper amount of explosives is involved. You do not wait 30 seconds.

You wait at least 30 minutes. But between a misfire and waiting is another step. But I don't know if that step is possible on a Hellcat. More modern tank guns have two firing systems. The normal one, and an emergency one. If there was a misfire you were supposed to try the emergency firing system next, and if that didn't work: Time to wait.

After waiting 30 minutes there are two things you can do. The first is to open the breech and check everything. Carry the round to a safe place, and blow it up. This is usually what you can do with normal, proper rounds. But in this case, with more shady ammunition I would go for option two: Call Ordnance. There are multiple things that could be wrong with the round, and I'm go out on a limb here and claim that the gunner did not have Ordnance training. In the military, if something goes wrong, Ordnance immediately becomes the supervisor of everything that happens. There might be Generals running around, but that mere Sarge (or whatever rank they have in the US) is in charge.
This is what Ordnance would most likely do:
- Establish what round is actually in the gun. Is it an original WW2 round, or is it aftermarket? What primer did they use? What powder? Is it an AP shell, or HE? Does the shell have a fuse? If yes, what type of fuse?
- Try to establish what happened with the round before it went into the gun. How was it stored? Did you put it in your shed, or in a bunker with AC?
This is all to determine one thing: Is the round stable? In other words: Can I move the round?

If the round is determined to be stable, Ordnance can do two things.
1. Open the breech from a safe distance, and making sure the round will be caught before it hits something. Considering an historic piece of equipment is involved, this can result in the best possible ending. Which is a round being ejected without problems. But it is possible that the round will detonate inside the vehicle, destroying the tank and sending shrapnel all over the place. For Ordnance, the problem isn't the tank being nuked, it's the shrapnel.

2. Remove the gun from the turret and move it to a safe place. Ordnance will put at least three shaped charges on the outside of the chamber. One aimed at the primer, one aimed at the propellant and the last one aimed at the shell itself. The whole barrel will then be covered with several tons of dirt and the charges detonated. Voila, another safe ending to a dangerous situation. The gun is properly ruined, but nobody is hurt (except maybe some feelings).

I'm assuming that the gunner knew how to handle firearms and various weapons. He had fired the gun before, he knows how it works. He might not have much experience with misfires, but he does know that he should wait a bit before opening the breech. But at this point, it's not a round you have in the gun. It's not a misfired round. It's not a nuisance. It's a faulty round.
It's an explosive. It intends to kill. And it intends to kill you. And it intends to kill you immediately.

Treat it as such. Don't touch anything. Sod off to a safe place. Call Ordnance.